Method of bonding light transmitting yarn to an



March 31, 1964 1.. THORINGTON 3,127,295

METHOD OF" BONDING LIGHT TRANSMITTING YARN TO AN INCANDESCENT LAMP ENVELOPE Filed Feb. 29, 1960 IN VEN T OR. 10%; five/mm 147 meme-r) United States Patent METHGD 0F BGNDENG LIGHT TRANSMIT- TING YARN TO AN HNCANDESCENT LAMP ENVELUPE Luke Thorington, Berkeley Heights, NJL, assignor to Burn-Test Corporation, North Bergen, N.J., a corporation of New York Filed Feb. 29, 1960, Ser. No. 11,902 4 Claims. (Cl. 156172) The invention herein disclosed comprises a process for the eificient manufacture of incandescent lamps having the construction disclosed in my copending application Serial No. 812,070, filed May 8, 1959, now Patent No. 2,963,612.

The objects of this invention are disclosed hereinafter in detail in connection with the specific descriptions of procedures by means of which these lamps can be efficiently manufactured.

In the accompanying drawings,

FIGURE 1 is an elevational view of an incandescent lamp of the type disclosed in said copending application, showing it partially completed;

FIGURE 2 is a cross sectional view taken on the line 22 of FIG. 1; and

FIGURE 3 is an elevational view partly in section of a yarn bundle as used in practicing the methods herein disclosed.

As illustrated in FIGS. 1 and 2, the lamp of this invention includes a suitable base, as for example the standard design screw threaded base 10, having the usual re-entrant stem and filament mount in suitable construction, neither of which are illustrated herein. Cemented to the base is an evacuated light transmitting envelope 12 consisting of a neck portion 14, a partially spherical portion 16 and a cylindrical dome shaped terminal portion 18.

The surface of the neck and spherical portions of the envelope is coated in any suitable manner by a normally tacky curable adhesive coating 22, on which is wrapped in contiguous convolutions 24 a light transmitting yarn bundle 20 to form a light modifying treatment therefor. The yarn bundle 20' is wound to the base of the terminal dome shaped portion 18 and then the winding is coated in any suitable manner with a light transmitting curable adhesive 2-6 to complete the lamp. As disclosed in the above mentioned copending application, surface treatment of this type produces mainly by refraction a novel flamelike image of the filament when energized. Even if the filament structure is concentrated more or less at the center of the spherical portion 16 of the lamp, its image appears through the retracting layer to be elongated so as to simulate the appearance of a candle or gas flame to a remarkable degree.

The purpose of this invention is to describe in the required detail several embodiments of procedures by means of which the manufacture of such lamps is facilitated.

While the yarn bundle 20 can be of a monofilament or multifilament construction and can be made of glass, clear plastics and the like, it should in overall dimensions be extremely fine so as to provide an image of such fine resolution as to appear to be continuous. With these thoughts in mind it is preferred to use fiber glass, which is known in the trade as electrical grade glass, consisting of a bundle of monofilaments. For example, the yarn bundle 20 will have an overall diameter of 0.0028" when composed of approximately 104 monofilaments of 0.00023" in diameter. Commonly a yarn of this type designated as 900 1/0 1 2 with a starch binder is suitable for the purpose. This yarn with its starch binder has a breaking strength of approximately 0.5 pound.

It is preferred that a multifilament yarn of this type be supplied in a yarn package consisting of a metal tube 30 having a plurality of perforations 32 distributed substantially throughout the length thereof. Wound on this tube is a practical quantity of the yarn bundle 20, which is received from the manufacturer as noted above with a starch binder.

The package illustrated in FIG. 3, sometimes called a cop, pirn or twister tube in accordance with preferable procedure, is placed in a horizontal position in a convection oven in which a temperature of approximately 650 F. is maintained for approximately forty-eight hours, after which it is removed from the oven and allowed to cool to room temperature. The purpose of this heat treatment is to clean 01f the starch binder which is applied to the yarn as an incident to its manufacture and packaging. When heated as explained above the starch binder is oxidized ofl the yarn. The perforated metal sleeve 30 facilitates the movement of hot air through the interior of the package to aid in its heat treatment.

The package is then subjected to an impregnation process wherein as a unit it is immersed in a solution of anhydrous isopropyl alcohol in which is dissolved 1% by volume of a solution containing 40% t butanol, 40% t amyl alcohol and 20% of the reaction product of one mol C H siCl with three mols of Z-dimethyl-aminoethanol (Le. HOCH CH NMe This reaction product is known to be a hydrochloride salt and is believed to have the formula C H Si OCH CH NMe HCl Immersion continues for a period of two to three hours to insure complete penetration of the solution into and through the bundle, which of course is facilitated by the perforated tubular support 30.

The impregnated package is then removed from the solution and transferred immediately to an autoclave where it is subjected, at atmospheric pressure, to steam until all the alcohol solvent has been removed. The period of treatment is relatively easy to determine and will vary, depending upon the size of the package being treated. When steaming of the package is completed it is placed in a drying oven and thoroughly dried, which takes approximately two hours, at a temperature of C. The yarn is now ready to be applied to the lamp. However, equivalent yarn package impregnating procedures will first be described.

In place of this silicone it is possible to use Dow Corning 200 Fluid in the concentration of 1% by volume in acetone to impregnate the yarn package. Dow Corning 200 Fluid is described by them as a trimethylsiloxy endblocked dimethylpolysiloxane. It has the general formula Me SiO(Me SiO) SiMe in which the viscosity of the material is obviously controlled by the average value of x in a particular polymeric mixture. Dow Corning 36 emulsion which is a water emulsion of the 200 Fluid can also be employed to impregnate the yarn package. This emulsion should be used in a concentration of approximately equal parts with water. This latter ingredient is stated to fall within the general scope of United States Patent 2,755,194.

Also Dow Corning 555 Fluid can be used to impregnate the yarn package. This is stated to be a liquid phenylmethylpolysiloxane, which those skilled in the art understand contains both phenyl and methyl radicals attached to silicon atoms in the polymer.

Before passing from this phase of the procedure it is noted that useful antistatic effects are produced by mixing with these various impregnates a suitable antistatic C9 agent such as Dow Corning Z6020 silicone which is a monomeric silane having the formula These ingredients are used in the solution in anhydrous isopropyl alcohol in equal proportions. By this procedure it is possible to prevent build-up of static electrical charges on the yarn during subsequent handling and wrapping on the bulb.

As the next step in the procedure the envelope 12 is coated in any suitable manner, as for example by dipping in Dow Corning 271 silicone adhesive consisting of a highly complex mixture of resinous and rubbery organopolysiloxanes in which the organic groups are methyl radicals and which contains xylene as a diluent and a small amount of lead octoate as a catalyst. This adhesive is dissolved in a suitable quantity of a solvent such as xylene. The quantity of the solvent is such as toprovide a solution of a viscosity suited to the purpose. This coating is shown in the drawings at 22 and provides a tacky surface on which the yarn hundle 20 can be wrapped either by fitting it to the lamp as it is revolved on its longitudinal axis, or by wrapping it around the lamp while stationary from a rotating flier. The winding takes place after the solvent xylene in this case has evaporated, which takes about thirty minutes, leaving the coating 22 tacky, as mentioned. In winding 21 900 1/0 yarn the pitch of the winding is approximately 6 mils. During the Winding the yarn hundle 20 should be under tension which is relatively light, and in the range of to 100 grams.

In supplying the yarn from the package to the winding position it is necessary, of course, that it be guided through eyelets or by other guide surfaces and in order to prevent build-up from the coating on the yarn on these guides it has been found that a fugitive lubricant such as Water is very effective. This lubricant tends to prevent build-up of the silicone on the guides and to reduce friction between such build-up as it is occurring and the coating on the wire wire passing through or over the guides.

After the lamp is fully wound a coating is applied over the winding by dipping, for example. A suitable coating for this purpose is Dow Corning A-4000 adhesive which is a highly complex mixture of resinous and rubbery organopolysiloxanes in which the organic groups are methyl radicals and which contains xylene as a diluent. Here again this adhesive is dissolved in a suitable solvent such as xylene to provide a solution of suitable viscosity. It is desirable to add to this solution a curing catalyst such as dibutyl tin Z-ethyl hexoate. The catalyst is dissolved in equal parts by weight xylene which solution is added to the adhesive in proportions of 4.5 parts by weight to 9 parts by weight per 100 parts of A-4000. The coated lamps are then allowed to stand at room temperature until the final coating has cured under the influence of the contained catalyst.

It is very important that the silicone adhesives used, that is the coatings 271 and A-4000, or their equivalents, be of such nature as not to penetrate the yarn bundle, and hence come into optical contact with the individual yarn filaments in the bundle. Optical contact between the yarn filaments and the coatings herein disclosed would completely destroy the optical effect for which the light transmitting yarns are used. This is true of the coatings used herein, including yarn package impregnates.

As will be apparent to those skilled in the art, whereti as coating or dipping has been mentioned, it will be understood that in suitable cases the coatings may be sprayed or brushed on.

It is also noted that although the yarn bundle 20 indicated in cross section as a monofilament is actually an assembly of approximately monofilaments mildly twisted together.

An important characteristic of the various compositions such as the coatings and adhesives herein disclosed is that of heat stability insofar as operating temperatures for incandescent lamps are involved. These coatings and adhesives after being set and cured should not soften or discolor in normal uses of the lamp and should be, as are the examples referred to, highly light transmitting to visible light so as not to cut down the light output.

In view of the above disclosure it will be apparent as to the nature of the objects of this invention and of the functions and purposes of the various steps and materials used. It will therefore follow that suitable equivalents will be apparent without departure from the novel subvject matter herein disclosed. It is proposed, therefore that the disclosure be accepted in a purely exemplary sense and that the scope of protection afforded hereby be determined by the appended claims.

What is claimed is:

1. The method of providing the light transmitting envelope of an incandescent lamp with a light modifying surface, comprising the steps of coating the lamp envelope with a xylene solution of a silicone adhesive, evaporating the solvent to leave said coating tacky, and Wrapping an extremely fine flexible light transmitting yarn onto the coated surface of said coated envelope to form a light refracting layer of contiguous convolutions of said yarn.

2. In the method of claim 1, said yarn being coated with a silicone and lubricating the coated yarn with water as it passes through guide members during wrapping.

3. In the method of claim 1, the additional step of coating said wrapping with a xylene solution of a silicone adhesive.

4. In the method of claim 1, the aditional step of coating said wrapping with a xylene solution of a complex mixture of resinous and rubbery organopolysiloxanes in which the organic groups are methyl radicals and which contains xylene as a diluent and a small amount of lead octoate as a catalyst.

References Cited in the file of this patent UNITED STATES PATENTS 597,964 Dunlap et al. Jan. 25, 1898 847,396 Bohm Mar. 19, 1907 1,720,968 Schmidt July 16, 1929 2,568,463 Reynolds Sept. 18, 1951 2,633,428 Klug Mar. 31, 1953 2,671,033 VVaggOner Mar. 2, 1954 2,686,737 Caroselli et al Aug. 17, 1954 2,694,661 Meyer Nov. 16, 1954 2,706,497 Shobert 2. Apr. 19, 1955 2,723,211 MacMullen et al Nov. 8, 1955 2,792,324 Daley et al May 14, 1957 2,799,598 Biefeld et al. July 16, 1957 FOREIGN PATENTS 210,608 Australia Oct. 4, 1957 342,289 Switzerland Dec. 31, 1959 807,133 Great Britain J an. 7, 1959 

1. THE METHOD OF PROVIDING THE LIGHT TRANSMITTING ENVELOP OF AN INCANDESCENT LAMP WITH ALIGHT MODIFYING SURFACE, COMPRISING THE STEPS OF COATING THE LAMP ENVELOPE WITH A XYLENE SOLUTION OF A SILICONE ADHESIVE, EVAPORATING THE SOLVENT TO LEAVE SAID COATING TACKY, AND WRAPPING AN EXTREMELY FINE FLEXIBLE LIGHT TRANSMITTING YARN ONTO THE COATED 